changed msi output directory

This changes the output directory of the MSI-setup to the \bin\MP2-Setup directory instead of the currently used subdir in \Setup\MP2-Setup\bin etc.

Compiling instructions have been updated in wiki: http://wiki.team-mediaportal.com/2_MEDIAPORTAL_2/Contribute/Development/Compiling

@gheitmann 
Changes required for the build server are documented in wiki as well: http://wiki.team-mediaportal.com/User:chefkoch/MediaPortal_2/BuildChanges/2_Location_of_*.MSI